A well centered anterior capsulotomy is an important factor in obtaining an optimal refractive outcome in intraocular lens (IOL) implantation, particularly for accommodating or pseudo accommodating IOLs, IOLs used to correct spherical aberration, or toric IOLs. The reason for this is that surgeons use the position of the capsular opening as a visual landmark to center the IOL. The centration is important both optically and mechanically. Optically, if the IOL, center of curvature of the cornea and fovea are not in proper alignment, image quality suffers from aberrations and mechanically, if the IOL is not centered with respect to the lens capsule equator, the lens may, over time, tilt or become more easily displaced, leading to optical aberrations or necessity of a secondary procedure to explant or re-center the IOL.
Currently, the anterior capsular opening is torn manually using a procedure known as continuous curvilinear capsulorhexis (CCC). In the absence of any other visual landmark, the opening is centered as well as can be accomplished manually, using the dilated pupil as the reference. Since the pupil is known to, on the average, dilate significantly asymmetrically, the current procedure, if successfully accomplished, tends to leave the IOL systematically off center with respect to the line of sight and the optic axis of the eye.
Ideally, the IOL should be centered on the visual axis; however, this cannot be determined intraoperatively. An alternative placement which can be determined and which allows IOL placement close to the natural state is to center the IOL such that the optical axes of the IOL and cornea be collinear. If the anterior capsulotomy cut can be positioned concentrically around the optic axis of the cornea and crystalline lens, i.e. such that the optic axis of the eye is maintained after implantation, then an IOL implanted and centered on the capsular opening would be close to optimally positioned.